Oh dear, a diary but no information! I'd say it's nute burn but then I have no information on which to make that statement! Do yourself (and us!) a favor and go edit at least the last week of your diary to include as much information as you can - especially about the nutes you're giving the plants! Meanwhile, if you ARE giving nutes, back off the strength a bit and definitely follow the water/feed/water/feed type of schedule - and when you water, make sure you're giving enough to each plant that about 10-20% is running off out the bottom.... Plants look pretty dry, tbh... and they look like they're in awfully small pots....
Good luck!